hrm... well, may be a noob answer but, Foes only boost magical damage, while Hypercharge can either be Physical or Magical depending on which turret you have out...

On the magical deparment it may be weaker, given the affected area size, and can't go higher than its 10%, unlike Foes that, added Battle Voice, doubles its effect potency.

However Foes does not offer any benefit for the caster himself, which Hypercharge's physical version actually do. It may be trickier to apply for AoE situations but its not like its impossible, and all the melees (including the tanks) will love it more than Foes.